The ATV isn't road legal so different emissions requirements apply. It's likely jetted noticeably richer which helps cold starting. Emissions requires also continue to get more stringent, so a 2007 might behave very differently from a 2017 of the same model.

This shall pass, be still and know.
2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.